The concept of handing over a communication from a first connection to a second connection is well known. There can be many reasons for performing such a handover, e.g. because the first connection deteriorates in quality due to the movement of the receiver, the sender associated with the first connection becomes overloaded, the second connection has became available and has more desirable properties, e.g. provides a higher data rate, etc.
Performing a handover from a first connection to a second connection means that the communication underway is discontinued over the first connection and continued over the second connection. It is possible that the second connection must first be established before performing the handover, and the first connection is itself discontinued after the handover, but this is not necessarily the case, as a handover can also be performed between standing connections whose existence is independent of the handover procedure.
One of the problems involved in handovers is that of data loss. Namely, in the course of transferring a communication from a first connection to a second connection, it is possible that parts of the data being transmitted to the sender are lost, e.g. because the data is queued or processed at the sender of the first connection, and was not completely transmitted at the time that the communication is discontinued over the first connection. In order to solve this problem, it has been suggested to perform so-called multicast handovers, in which prior to discontinuing the communication over the first (or old) connection, the data destined for the receiver is provided to both the sender of the first connection and the sender of the second (or new) connection.
It is noted that a handover scenario can comprise a plurality of second connections, i.e. that there can be several candidates to which the communication may be handed over. If this is the case, then the multicasting handover provides the data to all of the second connections.
As an example, if there are two access routers, each associated with its own access network, for wireless communication with a mobile receiver, where the connections from the access routers to the mobile are link layer connections or links, then the performance of a multicast handover can be implemented by having the first access router (the access of the first link from which the communication is being handed over) duplicate the layer 3 (i.e. above the link layer) data units (e.g. IP packets) that are to be sent to the mobile receiver, and forward these to the second access router (the access router of the second connection to which the communication is being handed over). The second access router queues the multicast data units, and starts sending upon receiving an appropriate enablement signal.